What is the midline equation of $y=8\cos\left(5\pi x+\dfrac{3\pi}{2}\right)-9$ ? $y=$
Midline in sinusoids of the form $y=a\cos(bx+c)+d$ Graphically, the midline of a sinusoidal function is the horizontal line that passes exactly in the middle of its extreme values. The midline equation of a sinusoid of the form $y={a}\cos(bx + c) + {d}$ is equal to $y={d}$. [How can we justify this given our graphical understanding of midline?] Finding the midline The midline equation of $y = 8\cos\left(5\pi x+\dfrac{3\pi}{2}\right){-9}$ is $y={-9}$.